JP4610867B2 - Method for manufacturing semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser irradiation apparatus and a laser irradiation method for activating a semiconductor film after crystallization or ion implantation using laser light.
[0002]
[Prior art]
In recent years, a technology for forming a TFT on a substrate has greatly advanced, and application development to an active matrix semiconductor display device has been advanced. In particular, a TFT using a polycrystalline semiconductor film has higher field effect mobility (also referred to as mobility) than a TFT using a conventional amorphous semiconductor film, and thus can operate at high speed. For this reason, it is possible to perform control of a pixel, which has been conventionally performed by a drive circuit provided outside the substrate, with a drive circuit formed on the same substrate as the pixel.
[0003]
By the way, as a substrate used for a semiconductor device, a glass substrate is considered promising from the viewpoint of cost rather than a single crystal silicon substrate. In general, a glass substrate is inferior in heat resistance and easily deforms by heat. Therefore, when a polysilicon TFT is formed on a glass substrate, laser annealing is used to crystallize a semiconductor film in order to avoid thermal deformation of the glass substrate. Used.
[0004]
The characteristics of laser annealing are that the processing time can be significantly shortened compared to annealing methods using radiation heating or conduction heating, and the semiconductor or semiconductor film is selectively and locally heated, causing thermal damage to the substrate. Things that are difficult to give are raised.
[0005]
The laser annealing method here refers to a technique for recrystallizing a damaged layer formed on a semiconductor substrate or a semiconductor film, or a technique for crystallizing a semiconductor film formed on a substrate. Moreover, the technique applied to planarization and surface modification of a semiconductor substrate or a semiconductor film is also included. The laser oscillation device to be applied is a gas laser oscillation device typified by an excimer laser, or a solid-state laser oscillation device typified by a YAG laser, and a semiconductor surface layer is irradiated with laser light for several tens of nano to several tens of microseconds. It is known to be crystallized by heating for a very short time.
[0006]
[Problems to be solved by the invention]
Lasers are roughly classified into two types, pulse oscillation and continuous oscillation, depending on the oscillation method. Since the pulsed laser has a relatively high output energy, the size of the laser beam (the area where the laser beam is actually irradiated on the surface of the workpiece) is several centimeters ² As described above, mass productivity can be improved. In particular, when the shape of the laser light is processed using an optical system to form a linear shape having a length of 10 cm or more, the substrate can be efficiently irradiated with the laser light, and mass productivity can be further improved. For this reason, it has become the mainstream to use a pulsed laser for crystallization of the semiconductor film.
[0007]
However, in recent years, it has been found that the crystal grain size formed in a semiconductor film is larger when a continuous wave laser is used than when a pulsed laser is used for crystallization of a semiconductor film. As the crystal grain size in the semiconductor film increases, the mobility of TFTs formed using the semiconductor film increases. For this reason, continuous wave lasers are starting to attract attention.
[0008]
However, a continuous wave laser generally has a smaller maximum output energy than a pulsed laser. The size of the laser beam is 10 ^-3 mm ² If it is made small, the desired power necessary for crystallization of the semiconductor film can be obtained. However, since the area of the laser beam is small, the scanning time of the laser beam per substrate is long, and the substrate processing efficiency is poor.
[0009]
Conversely, if the area of the laser beam is increased in order to increase the substrate processing efficiency, the energy density naturally decreases. In order to give the semiconductor film a total amount of heat necessary for crystallization, it is necessary to lengthen the irradiation time, and the irradiation time of the laser light per area on the substrate becomes longer. Then, the substrate is heated by heat conduction from the absorption of the laser light into the semiconductor film, the substrate itself is thermally deformed, and the characteristics of the TFT are easily deteriorated due to the diffusion of impurities from the glass substrate to the semiconductor film. When the substrate is heated, the crystallinity of the semiconductor film is difficult to be uniform due to the heat accumulated in the substrate, and the characteristics of the TFT are likely to vary.
[0010]
In view of the above-described problems, the present invention can increase the efficiency of substrate processing as compared with the prior art, and can suppress thermal damage to the substrate, and a laser using the laser crystallization method It is an object to provide an irradiation apparatus.
[0011]
[Means for Solving the Problems]
The laser irradiation apparatus according to the present invention includes a plurality of first means (laser oscillation apparatus) for oscillating laser light, and condensing the laser light oscillated from the plurality of laser oscillation apparatuses, and further, laser light on the object to be processed. A second means (optical system) for partially superimposing each other, a slit capable of shielding a part of the synthesized laser beam, and an object to be processed irradiated through the slit And a third means for controlling the position of the laser beam. Furthermore, the present invention controls the oscillation of each of the plurality of first means, and the position of the laser light whose shape is controlled by the slit in the workpiece, the plurality of laser oscillation devices and the third means. You may have the 4th means controlled by synchronizing.
[0012]
By synthesizing laser beams oscillated from a plurality of laser oscillation devices, it is possible to compensate for the weak energy density of each laser beam. Therefore, rather than combining laser beams emitted from a plurality of laser oscillation devices without using them individually, a region of the laser beam having an energy density required for crystallization is widened, and the substrate processing efficiency is increased. Can be increased.
[0013]
Further, in the present invention, a slit is used to cut a region of the synthesized laser light whose energy density is less than a predetermined height in the scanning direction. With the above configuration, the average value of the energy density of laser light in the scanning direction can be increased, the irradiation time of laser light per area can be suppressed, and the total amount of heat given to the object to be processed can be increased. Therefore, the crystallinity of the semiconductor film can be improved while suppressing the substrate from being heated.
[0014]
In addition, after the semiconductor film is formed, laser light irradiation is performed so that the semiconductor film is not crystallized so that the semiconductor film is not exposed to the air (for example, a specified gas atmosphere such as a rare gas, nitrogen, oxygen, or a reduced pressure atmosphere). Also good. With the above configuration, contaminants at the molecular level in the clean room, such as boron contained in a filter for increasing the cleanliness of air, can be prevented from being mixed into the semiconductor film during crystallization by laser light. it can.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the structure of the laser irradiation apparatus of this invention is demonstrated using FIG. Reference numeral 101 denotes a laser oscillation device. In FIG. 1, four laser oscillation devices are used, but the laser irradiation device of the present invention may have a plurality of laser oscillation devices, and the number is not limited to this.
[0016]
The laser can be appropriately changed depending on the purpose of processing. In the present invention, a known laser can be used. Further, it is not limited to continuous oscillation, and pulse oscillation can be used, and a gas laser or a solid laser may be used. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. _Four Laser, YLF laser, YAlO _Three Laser, glass laser, ruby laser, alexandride laser, Ti: sapphire laser, Y ₂ O _Three Etc. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. _Four , YLF, YAlO _Three Lasers using crystals such as are applied. The fundamental wave of the laser differs depending on the material to be doped, and a laser beam having a fundamental wave of about 1 μm can be obtained. The harmonic with respect to the fundamental wave can be obtained by using a nonlinear optical element.
[0017]
Furthermore, after converting infrared laser light emitted from a solid-state laser into green laser light by a nonlinear optical element, ultraviolet laser light obtained by another nonlinear optical element can also be used.
[0018]
Note that the laser oscillation device 101 may use a chiller 102 to keep the temperature constant. Although the chiller 102 is not necessarily provided, by keeping the temperature of the laser oscillation device 101 constant, it is possible to suppress the energy of the output laser light from varying depending on the temperature.
[0019]
Reference numeral 104 denotes an optical system that can focus the laser beam by changing the optical path output from the laser oscillation device 101 or by processing the shape of the laser beam. Furthermore, what is important in the optical system 104 of the present invention is that the laser beams of the laser beams output from the plurality of laser oscillation devices 101 can be partially overlapped and synthesized.
[0020]
Note that an AO modulator 103 capable of changing the traveling direction of the laser light may be provided in an optical path between the substrate 106 that is an object to be processed and the laser oscillation device 101.
[0021]
The synthesized laser light is applied to the substrate 106 that is an object to be processed through the slit 105. The slit 105 is preferably formed of a material that can partially block the laser beam and that is not deformed or damaged by the laser beam. The slit 105 may have a variable width of the opening through which the laser beam passes (hereinafter referred to as the slit width), and the width of the laser beam in the scanning direction can be controlled by the width of the slit.
[0022]
Note that the shape of the laser light on the substrate 106 of the laser light oscillated from the laser oscillation device 101 when not passing through the slit 105 differs depending on the type of laser, and can also be formed by an optical system.
[0023]
The substrate 106 is placed on the stage 107. In FIG. 1, the position control means 108 and 109 correspond to means for controlling the position of the laser beam on the workpiece, and the position of the stage 107 is controlled by the position control means 108 and 109. In FIG. 1, by changing the position of the substrate using the position control means 108 and 109, the laser light can be moved (scanned) and the scanning direction of the laser light can be changed. The position control means 108 controls the position of the stage 107 in the X direction, and the position control means 109 controls the position of the stage 107 in the Y direction.
[0024]
Further, the laser irradiation apparatus of the present invention may have a computer 110 having both a central processing unit and storage means such as a memory. The computer 110 can control the oscillation of the laser oscillation device 101 and also control the position control means 108 and 109 to set the substrate at a predetermined position. The width of the slit 105 may be controlled by the computer 110.
[0025]
Furthermore, the laser irradiation apparatus of the present invention may include means for adjusting the temperature of the object to be processed. Further, since the laser light is light having high directivity and energy density, a damper may be provided to prevent the reflected light from being irradiated to an inappropriate place. The damper desirably has a property of absorbing reflected light, and cooling water may be circulated in the damper to prevent the temperature of the partition wall from rising due to absorption of the reflected light. Further, a means for heating the substrate (substrate heating means) may be provided on the stage 107.
[0026]
In addition, one CCD camera 113 may be provided for positioning the substrate 106, and in some cases, several CCD cameras 113 may be provided.
[0027]
Next, the shape of the laser beam synthesized by superimposing a plurality of laser beams will be described.
[0028]
FIG. 2A shows an example of the shape of laser light before synthesis. The laser beam shown in FIG. 2A has an elliptical shape. In the laser irradiation apparatus of the present invention, the shape of the laser beam is not limited to an ellipse. The shape of the laser light varies depending on the type of laser, and can also be shaped by an optical system. For example, the shape of a laser beam emitted from a Lambda XeCl excimer laser (wavelength 308 nm, pulse width 30 ns) L3308 is a rectangular shape of 10 mm × 30 mm (both half-value width in the beam profile). The shape of the laser light emitted from the YAG laser is circular if the rod shape is cylindrical, and rectangular if it is slab type. By further shaping such laser light with an optical system, laser light of a desired size can be produced.
[0029]
FIG. 2B shows the energy density distribution of the laser light in the major axis Y direction of the laser light shown in FIG. The distribution of the energy density of the laser beam having an elliptical laser beam becomes higher toward the center O of the ellipse.
[0030]
Next, the shape of the laser light when the laser light is synthesized is shown in FIG. Note that FIG. 2C illustrates the case where one laser beam is formed by superimposing four laser beams, but the number of laser beams to be superimposed is not limited thereto.
[0031]
As shown in FIG. 2C, the laser beams of the respective laser beams are synthesized by matching the major axes of the respective ellipses and overlapping a part of the laser beams to form one laser beam. . Hereinafter, a straight line obtained by connecting the centers O of the ellipses is referred to as a central axis.
[0032]
FIG. 2D shows the energy density distribution of the laser light in the central axis direction of the combined laser light shown in FIG. The energy density is added at the portion where the laser beams before synthesis overlap. For example, when the energy densities A and B of the overlapping beams are added as shown in the figure, the peak value C of the energy density of the beams is approximately equal, and the energy density is flattened between the centers O of the ellipses.
[0033]
Note that when A and B are added, it is ideally equal to C, but in reality, it is not necessarily equal. The deviation between the value obtained by adding A and B and the value of C should be within ± 10%, more preferably within ± 5% of the value of C, but the allowable range can be set appropriately by the designer. is there.
[0034]
As can be seen from FIG. 2D, by superimposing a plurality of laser beams and complementing each other with a low energy density, the semiconductor film can be formed more than using a plurality of laser beams without overlapping. Crystallinity can be increased efficiently. For example, it is assumed that the energy density necessary for obtaining the desired crystal is satisfied only in the region indicated by the oblique lines in FIG. 2A, and the energy density is not satisfied to the desired value in the other regions. In this case, each laser beam can obtain a desired crystal only in the shaded area indicated by the width m in the central axis direction. However, by superimposing laser beams as shown in FIG. 2D, a desired crystal can be obtained in a region where the width in the central axis direction is represented by n (n> 4 m), and the semiconductor is more efficiently produced. The film can be crystallized.
[0035]
Furthermore, in the present invention, a region where the energy density does not reach a desired value in the direction perpendicular to the central axis of the laser beam is shielded by the slit 105. The positional relationship between the synthesized laser beam and the slit will be described with reference to FIG.
[0036]
The slit 105 used in the present invention may have a variable slit width, and the computer 110 may control the width. In FIG. 3A, reference numeral 120 denotes the shape of laser light obtained by the synthesis shown in FIG. In the laser beam 120, a region where the energy density satisfies a predetermined value is indicated by 120a, and a region where the energy density does not reach is indicated by 120b. Reference numeral 105 denotes a slit. FIG. 3A shows a state where the laser beam 120 is not shielded by the slit.
[0037]
FIG. 3B shows a state of laser light partially blocked by the slit 105. As shown in FIG. 3B, in the present invention, the region 120 b that is present across the region 120 a in the direction perpendicular to the central axis of the laser beam 120 is shielded by the slit 105. FIG. 3C shows an energy density distribution at AA ′ perpendicular to the central axis of the laser beam shown in FIG. 3B, and at least the energy density is a predetermined height (eg, T). It can be seen that the area that has not been reached is blocked by the slit 105.
[0038]
With the above structure, the average value of the energy density of the laser light in the direction perpendicular to the central axis can be increased, and the irradiation time of the laser light at any point on the object to be processed can be suppressed. Therefore, the crystallinity of the semiconductor film can be improved while suppressing the substrate from being heated.
[0039]
In the present invention, the region 120b existing between the regions 120a in the direction of the central axis of the laser beam may be shielded by the slit 105. FIG. 4A shows a state in which the region 120b existing across the region 120a is shielded by the slit 105 in the central axis direction of the laser light. Further, FIG. 4B shows an energy density distribution in the central axis direction of the laser light shown in FIG. As shown in FIG. 4B, it can be seen that at least a region where the energy density does not satisfy a predetermined height (for example, T) is shielded by the slit 105.
[0040]
A semiconductor film crystallized by a region having a low energy density has poor crystallinity. Specifically, the crystal grains are smaller than the region where the predetermined energy density is satisfied, or the directions in which the crystal grains grow are different. Therefore, it is necessary to determine the scanning path of the laser beam and the layout of the active layer so that the region having a low energy density does not overlap with an active layer to be formed later. By using the laser beam having the energy density distribution shown in FIG. 4B, a region having a low energy density does not exist or becomes narrow, so that restrictions on the scanning path of the laser beam and the layout of the active layer are reduced. can do.
[0041]
In addition, since the shape of the laser beam can be changed without stopping the output of the laser oscillation device while keeping the energy density constant, it is possible to prevent the edge of the laser beam from overlapping the active layer or its channel formation region. it can. Further, unnecessary portions can be irradiated with laser light to prevent the substrate from being damaged.
[0042]
Next, the scanning direction of the laser light in the semiconductor film 150 which is formed to manufacture an active matrix semiconductor device will be described with reference to FIG. In FIG. 5A, a region 151 surrounded by a broken line corresponds to a pixel portion, a region 152 corresponds to a signal line driver circuit, and a region 153 corresponds to a portion where a scanning line driver circuit is formed.
[0043]
In FIG. 5A, the substrate is moved in the direction of the white arrow, and the solid line arrow indicates the relative scanning direction of the laser light. FIG. 5B is an enlarged view of the laser beam 154 in the portion 151 where the pixel portion is formed. An active layer 155 is formed in the region irradiated with the laser light.
[0044]
Although FIG. 5 shows the case where the central axis direction of the laser beam and the scanning direction are kept perpendicular, the central axis of the laser beam and the scanning direction are not necessarily perpendicular. For example, the acute angle θ formed between the central axis of the laser beam and the scanning direction _A May be 45 ° ± 35 °, and more preferably 45 °. When the central axis of the laser beam is perpendicular to the scanning direction, the substrate processing efficiency is most enhanced. On the other hand, the scanning direction and the center of the laser beam are obtained by scanning so that the central axis of the combined laser beam and the scanning direction are 45 ° ± 35 °, preferably closer to 45 °. Compared to scanning with the axis perpendicular, the number of crystal grains present in the active layer can be intentionally increased, and variations in characteristics due to crystal orientation and crystal grains can be reduced. Can do.
[0045]
Furthermore, in the present invention, the computer 110 in FIG. 1 may determine a portion to scan with laser light according to mask pattern information. In this case, the computer 110 partially crystallizes the semiconductor film by controlling the position control means 108 and 109 so that the laser beam hits a predetermined scanning portion. Accordingly, the laser light can be scanned so that the indispensable portion can be crystallized at the minimum, so that it is not necessary to irradiate the entire surface of the substrate with the laser light, and the substrate processing efficiency can be improved.
[0046]
Note that when the crystallized semiconductor film is used as an active layer of a TFT, it is desirable that the scanning direction of the laser light be parallel to the direction in which the carriers in the channel formation region move.
[0047]
An example of the relationship between the scanning direction of laser light applied to a semiconductor film formed in order to fabricate an active matrix semiconductor device and the layout of active layers in each circuit will be described with reference to FIGS.
[0048]
In FIG. 6, a semiconductor film 850 is formed on a substrate. A portion surrounded by a broken line 853 is a portion where a pixel portion is formed, and a portion 856 serving as a plurality of active layers is provided in the pixel portion. A portion surrounded by a broken line 854 is a portion where a signal line driver circuit is formed, and portions 857 serving as a plurality of active layers are provided in the signal line driver circuit. A portion surrounded by a broken line 855 is a portion where a scanning line driver circuit is formed, and a portion 858 serving as a plurality of active layers is provided in the scanning line driver circuit.
[0049]
Note that the portions 856, 857, and 858, which are active layers included in each circuit, are actually several tens of μm in size and smaller than those shown in FIG. For the sake of illustration, it was greatly illustrated. The portions 856, 857, and 858 that serve as active layers included in each circuit are laid out so that carriers in the channel formation region move in a certain direction.
[0050]
The portion 851 that is crystallized by laser light irradiation covers the portions 856, 857, and 858 that are all active layers. The moving direction of the laser light is aligned with the direction in which the carriers in the channel formation region move.
[0051]
【Example】
Examples of the present invention will be described below.
[0052]
Example 1
A crystalline semiconductor film formed by irradiating laser light is formed by aggregating a plurality of crystal grains. The position and size of the crystal grains are random, and it is difficult to form a crystalline semiconductor film by specifying the position and size of the crystal grains. Therefore, there are cases where crystal grain interfaces (grain boundaries) exist in the active layer formed by patterning the crystalline semiconductor into islands.
[0053]
Unlike crystal grains, there are innumerable recombination centers and trap centers due to amorphous structures and crystal defects at grain boundaries. It is known that when carriers are trapped in this trapping center, the potential of the grain boundary increases and becomes a barrier against the carriers, so that the current transport characteristics of the carriers are reduced. Therefore, if there is a grain boundary in the active layer of the TFT, particularly in the channel formation region, the mobility of the TFT is remarkably reduced, and the current flows at the grain boundary, resulting in an increase in off current. Serious effect. In addition, in a plurality of TFTs manufactured on the assumption that the same characteristics can be obtained, the characteristics vary depending on the presence or absence of grain boundaries in the active layer.
[0054]
The reason why the position and size of the obtained crystal grains are random when the semiconductor film is irradiated with laser light is as follows. Crystallization of the liquid semiconductor film melted by laser light irradiation proceeds as the solid-liquid interface moves from a relatively low temperature region to a high temperature region over time in the film. When the entire surface of the semiconductor film is irradiated with laser light, the temperature of the semiconductor film is relatively uniform in the horizontal direction (hereinafter referred to as the lateral direction) with respect to the film surface, but the temperature is closer to the surface in the film thickness direction. A temperature gradient is generated such that becomes higher. For this reason, the crystal grows by moving the interface between the solid and the liquid toward the surface from the crystal nucleus existing in the region having a relatively low temperature far from the surface of the semiconductor film. The positions where the crystal nuclei are present are random in the lateral direction, and the crystal growth ends when the crystal grains collide with each other, so that the position and size of the crystal grains are random.
[0055]
On the other hand, rather than melting the semiconductor film in a relatively wide area and forming a temperature gradient in the film thickness direction, by partially melting the semiconductor film and forming the temperature gradient in the lateral direction, the crystalline semiconductor film There has also been proposed a method of forming the film. In this case, the moving direction of the interface between the solid and the liquid in the semiconductor film can be controlled so as to be a lateral direction rather than a film thickness direction. Therefore, since the crystal growth direction can be aligned with the lateral direction having a temperature gradient, the crystal grains grow to a length of several tens of times the film thickness. Hereinafter, this phenomenon is referred to as super lateral growth.
[0056]
In the case of the super lateral growth, relatively large crystal grains can be obtained and the number of grain boundaries is reduced. However, the energy range of the laser beam realized by the super lateral growth is very narrow, and large crystal grains can be obtained. It was difficult to control the position. Further, the region other than the large crystal grains was a microcrystalline region where innumerable nuclei were generated or an amorphous region.
[0057]
Therefore, if the laser beam in the energy region that completely melts the semiconductor film can be used and the temperature gradient in the lateral direction can be controlled, the growth position and growth direction of the crystal grains can be controlled. It is considered. Various attempts have been made to realize this method.
[0058]
For example, James S. Im and others of Columbia University have shown a Sequential Lateral Solidification method (hereinafter referred to as SLS method) that can realize super lateral growth in any place. In the SLS method, crystallization is performed by shifting the slit-shaped mask for each shot by a distance (about 0.75 μm) at which super lateral growth is performed.
[0059]
In the present embodiment, an example in which the SLS method is applied to the present invention will be described.
[0060]
First, the semiconductor film 802 is irradiated with the first shot of laser light. The first shot laser light uses a pulsed laser and is irradiated at an energy density that can locally melt the semiconductor film over the entire thickness.
[0061]
FIG. 7A schematically shows the state of the semiconductor film 802 immediately after the first shot is irradiated. By irradiation with the first shot of laser light, the semiconductor film locally melts over the entire thickness in the portion of the semiconductor film 802 where the laser light 801 is irradiated.
[0062]
At this time, in the portion of the semiconductor film 802 where the laser light is applied, the semiconductor is completely melted. However, the portion where the laser light is not applied is not melted, or the temperature is the laser even if it is melted. It is sufficiently low compared to the part that is exposed to light. Therefore, the end portion of the laser beam becomes a seed crystal, and the crystal grows in a lateral direction from the end portion of the laser beam toward the center as indicated by an arrow.
[0063]
As the growth of the crystal progresses over time, it collides with the crystal grains generated from the seed crystal generated in the completely melted part, or collides with the crystal grains grown from the opposite side. Crystal growth ends at the central portion 803 of the laser beam. FIG. 7B schematically shows the state of the semiconductor film when the crystal growth is completed. In the central portion 803 of the laser light, a larger number of microcrystals are present than in other portions, and the surface of the semiconductor film is irregular because crystal grains collide with each other.
[0064]
Next, the second shot is irradiated. The second shot is irradiated with a slight shift from the laser light of the first shot. FIG. 7C schematically shows the state of the semiconductor film immediately after the second shot is irradiated. Although the position of the second-shot laser beam is shifted from the portion 801 where the first-shot laser beam was hit, in FIG. 7C, the center at which the second-shot laser beam was formed by the first shot. This is a deviation that covers the portion 803.
[0065]
At this time, the semiconductor is completely melted in the portion where the second shot of the laser beam 804 is hit, but the portion not hit by the laser beam is not melted, or the temperature is kept even if it is melted. It is sufficiently low compared to the part that is exposed to the laser beam. Therefore, the end portion of the laser beam becomes a seed crystal, and the crystal grows in a lateral direction from the end portion of the laser beam toward the center as indicated by an arrow. At this time, in the portion 801 crystallized by the first shot, the portion not irradiated with the laser light of the second shot becomes a seed crystal, and the crystal grown in the lateral direction formed by the first shot further moves in the scanning direction. Grows towards.
[0066]
As the growth of the crystal progresses over time, it collides with the crystal grains generated from the seed crystal generated in the completely melted part, or collides with the crystal grains grown from the opposite side. Crystal growth ends at the central portion 805 of the second shot of laser light. FIG. 7D schematically shows the state of the semiconductor film when the crystal growth is completed. In the central portion 805 of the laser beam, a larger number of microcrystals are present than in other portions, or the surface of the semiconductor film is irregular because crystal grains collide with each other.
[0067]
Similarly, the third and subsequent shots are similarly irradiated with the laser beam shifted in the scanning direction little by little, so that a crystal grows in parallel with the scanning direction as shown in FIG.
[0068]
With the above configuration, crystallization can be partially performed while controlling the position and size of crystal grains.
[0069]
Next, an example different from FIG. 7 in which the SLS method is applied to the present invention will be described.
[0070]
First, the semiconductor film 812 is irradiated with the first shot of laser light. As the laser light, a pulsed laser is used, and irradiation is performed at an energy density that can locally melt the semiconductor film over the entire thickness at a portion determined by the mask.
[0071]
FIG. 8A schematically shows the state of the semiconductor film immediately after the first shot is irradiated. By irradiation with the first shot of laser light, the semiconductor film is locally melted over the entire thickness in the portion of the semiconductor film 812 where the laser light 811 is irradiated. The end portion of the laser beam becomes a seed crystal, and the crystal grows in the lateral direction from the end portion of the laser beam toward the center as indicated by an arrow.
[0072]
As the growth of the crystal progresses over time, it collides with the crystal grains generated from the seed crystal generated in the completely melted part, or collides with the crystal grains grown from the opposite side. Crystal growth ends at the central portion 813 of the laser beam. FIG. 8B schematically shows the state of the semiconductor film when the crystal growth is completed. In the central portion 813 of the laser beam, a larger number of microcrystals are present than in other portions, or the surface of the semiconductor film is irregular because crystal grains collide with each other.
[0073]
Next, the second shot is irradiated. The second shot is irradiated with a slight shift from the laser light of the first shot. FIG. 8C schematically shows the state of the semiconductor film immediately after the second shot is irradiated. Although the position of the laser beam for the second shot is shifted from the portion 811 where the laser beam for the first shot was hit, in FIG. 8C, the center where the laser beam for the second shot was formed by the first shot. The portion 813 is not covered, and the displacement is such that it partially overlaps the portion that was hit by the laser light of the first shot.
[0074]
The end portion of the laser light in the second shot becomes a seed crystal, and the crystal grows in a lateral direction from the end portion of the laser light toward the center as indicated by an arrow. At this time, in the portion 811 crystallized by the first shot, the portion not irradiated with the laser light of the second shot becomes a seed crystal, and the crystal grown in the lateral direction formed by the first shot further moves in the scanning direction. Grows towards.
[0075]
As the growth of the crystal progresses over time, it collides with the crystal grains generated from the seed crystal generated in the completely melted part, or collides with the crystal grains grown from the opposite side. Crystal growth ends at the central portion 815 of the second shot of laser light. FIG. 8D schematically shows the state of the semiconductor film when the crystal growth is completed. In the central portion 815 of the laser light, a larger number of microcrystals are present than in other portions, and the surface of the semiconductor film is irregular because crystal grains collide with each other.
[0076]
Similarly, the third and subsequent shots are similarly irradiated with laser light that is gradually shifted in the scanning direction, so that a crystal grows in parallel with the scanning direction as shown in FIG. With the above configuration, crystallization can be partially performed while controlling the position and size of crystal grains.
[0077]
In the crystal obtained by the irradiation method shown in FIG. 8, the central portion of the laser beam is left, and the crystallinity is not good in the central portion, so that the central portion is not included in the channel formation region. Preferably, the active layer is laid out so as not to be included in the active layer.
[0078]
Note that in both of the irradiation methods in FIGS. 7 and 8, if the active layer is laid out so that the growth direction of crystal grains and the direction of carriers in the channel formation region are parallel to each other, the channel formation region is included. Since less grain boundaries are generated, mobility is increased and off-current can be suppressed. Further, when the active layer is laid out so that the carrier traveling direction and the crystal grain growth direction in the channel formation region are not parallel to each other, the grain boundaries included in the channel formation region increase. However, when a plurality of active layers are compared, the ratio of the difference in the amount of grain boundaries between active layers with respect to the total grain boundaries included in the channel formation region of each active layer becomes small, and the mobility and The variation in the off-current value is reduced.
[0079]
The laser can be an excimer laser or a YLF laser, but the type of laser is not limited to this configuration.
[0080]
In the SLS method shown in the present embodiment, it is necessary to locally melt the semiconductor film over the entire thickness in the portion irradiated with the laser beam. In the laser irradiation apparatus or the laser irradiation method of the present invention, the average value of the energy density of the laser beam in the scanning direction can be increased, so that the irradiation time of the laser beam per area can be reduced during crystallization using the SLS method. The semiconductor film can be locally melted over the entire thickness while suppressing the substrate from being heated.
[0081]
(Example 2)
In this embodiment, an optical system for superimposing laser beams will be described.
[0082]
FIG. 9 shows a specific configuration of the optical system of the present embodiment. 9A is a side view of the optical system of the laser irradiation apparatus of the present invention, and FIG. 9B shows a side view seen from the direction of arrow B in FIG. 9A. Note that a side view seen from the direction of arrow A in FIG. 9B corresponds to FIG.
[0083]
FIG. 9 shows an optical system when four laser beams are combined into one laser beam. Note that the number of laser beams to be synthesized in this embodiment is not limited to this, and the number of laser beams to be synthesized may be 2 or more and 8 or less.
[0084]
Reference numerals 401, 402, 403, 404, and 405 denote cylindrical lenses. Although not shown in FIG. 9, the optical system of the present embodiment uses six cylindrical lenses. FIG. 10 is a perspective view of the optical system shown in FIG. Laser light is incident on each of the cylindrical lenses 403, 404, 405, and 406 from different laser oscillation devices.
[0085]
Laser light whose shape is processed by the cylindrical lenses 403 and 405 enters the cylindrical lens 401. The incident laser light is processed by a cylindrical lens, and then a part of the laser light is cut by the slit 410 and irradiated onto the workpiece 400. In addition, laser light whose shape is processed by the cylindrical lenses 404 and 406 is incident on the cylindrical lens 402. The incident laser light is processed by a cylindrical lens, and then a part of the laser light is cut by the slit 410 and irradiated onto the workpiece 400.
[0086]
The laser beams of the laser beam in the workpiece 400 are combined by overlapping each other to form one laser beam.
[0087]
In this embodiment, the focal lengths of the cylindrical lenses 401 and 402 closest to the workpiece 400 are 20 mm, and the focal lengths of the cylindrical lenses 403 to 406 are 150 mm. Then, the incident angle θ of the laser beam from the cylindrical lenses 401 and 402 to the workpiece 400 ₁ Is 25 ° in the present embodiment, and the incident angle θ of the laser beam from the cylindrical lenses 403 to 406 to the cylindrical lenses 401 and 402 is θ. ₂ Each lens is set so that the angle is 10 °.
[0088]
The focal length and incident angle of each lens can be set as appropriate by the designer. Furthermore, the number of cylindrical lenses is not limited to this, and the optical system used is not limited to cylindrical lenses. The present invention processes the laser light of the laser light oscillated from each laser oscillation device so as to have a shape and energy density suitable for crystallization of a semiconductor film, and superimposes the laser light of all laser lights on each other. Any optical system can be used as long as they can be combined into a single laser beam.
[0089]
In this embodiment, an example in which four laser beams are synthesized is shown. In this case, four cylindrical lenses respectively corresponding to the four laser oscillation devices and two cylindrical lenses corresponding to the four cylindrical lenses are provided. Have. When synthesizing n (n = 2, 4, 6, 8) laser beams, n cylindrical lenses respectively corresponding to the n laser oscillation devices, and n / 2 cylindrical lenses corresponding to the n cylindrical lenses, have. When synthesizing n (n = 3, 5, 7) laser beams, n cylindrical lenses respectively corresponding to the n laser oscillation devices, and (n + 1) / 2 cylindrical lenses corresponding to the n cylindrical lenses, have.
[0090]
Next, the optical system of the laser irradiation apparatus of the present invention using eight laser oscillation apparatuses will be described.
[0091]
11 and 12 show a specific configuration of an optical system used in the laser irradiation apparatus of this embodiment. 11 is a side view of the optical system of the laser irradiation apparatus of the present invention, and FIG. 12 shows a side view seen from the direction of arrow B in FIG. A side view seen from the direction of arrow A in FIG. 12 corresponds to FIG.
[0092]
In this embodiment, an optical system in the case where eight laser beams are combined into one laser beam is shown. Note that the number of laser beams to be synthesized in the present invention is not limited to this, and the number of laser beams to be synthesized may be 2 or more and 8 or less.
[0093]
Reference numerals 441 to 450 denote cylindrical lenses, which are not shown in FIGS. 11 and 12, but the optical system of this embodiment uses twelve cylindrical lenses 441 to 452. FIG. 13 is a perspective view of the optical system shown in FIGS. Laser light is incident on each of the cylindrical lenses 441 to 444 from a different laser oscillation device.
[0094]
Then, the laser light whose shape is processed by the cylindrical lenses 450 and 445 enters the cylindrical lens 441. The incident laser light is processed by the cylindrical lens 441 and then a part of the laser light is cut by the slit 460 and irradiated to the object 440. In addition, laser light whose shape is processed by the cylindrical lenses 451 and 446 is incident on the cylindrical lens 442. After the shape of the laser beam is processed by the cylindrical lens 442, a part of the incident laser beam is cut by the slit 460 and irradiated to the object 440. In addition, laser light whose shape is processed by the cylindrical lenses 449 and 447 is incident on the cylindrical lens 443. After the shape of the laser beam is processed by the cylindrical lens 443, a part of the incident laser beam is cut by the slit 461 and irradiated to the object 440. In addition, laser light whose shape is processed by the cylindrical lenses 452 and 448 is incident on the cylindrical lens 444. After the shape of the laser beam is processed by the cylindrical lens 444, a part of the incident laser beam is cut by the slit 461 and irradiated on the workpiece 440.
[0095]
The laser beams of the laser beam in the object to be processed 440 are synthesized by overlapping each other to form one laser beam.
[0096]
In this embodiment, the focal lengths of the cylindrical lenses 441 to 444 closest to the workpiece 440 are set to 20 mm, and the focal lengths of the cylindrical lenses 445 to 452 are set to 150 mm. Then, the incident angle θ of the laser beam from the cylindrical lenses 441 to 444 to the object 440 to be processed. ₁ Is 25 ° in this embodiment, and the incident angle θ of the laser beam from the cylindrical lenses 445 to 452 to the cylindrical lenses 441 to 444 is ₂ Each lens is set so that the angle is 10 °.
[0097]
The focal length and incident angle of each lens can be set as appropriate by the designer. Furthermore, the number of cylindrical lenses is not limited to this, and the optical system used is not limited to cylindrical lenses. The present invention processes the laser light of the laser light oscillated from each laser oscillation device so as to have a shape and energy density suitable for crystallization of a semiconductor film, and superimposes the laser light of all laser lights on each other. Any optical system can be used as long as they can be combined into a single laser beam.
[0098]
In this embodiment, an example of synthesizing eight laser beams is shown. In this case, eight cylindrical lenses respectively corresponding to the eight laser oscillation devices and four cylindrical lenses corresponding to the eight cylindrical lenses are provided. Have.
[0099]
When superposing five or more laser beams, considering the arrangement of the optical system, it is desirable to irradiate the fifth and subsequent laser beams from the opposite side of the substrate. In this case, the substrate is transparent to the laser beam. It is necessary to do.
[0100]
In order to achieve uniform laser light irradiation, a plane or long side that is a plane perpendicular to the irradiation surface and includes a short side when the shape of each beam before synthesis is regarded as a rectangle is used. If any one of the surfaces to be included is defined as an incident surface, the incident angle θ of the laser light is set such that the length of the short side or the long side included in the incident surface is W, and is set on the irradiation surface, and It is desirable that θ ≧ arctan (W / 2d) is satisfied when the thickness of the substrate having translucency with respect to the laser beam is d. This argument needs to hold for each laser beam before synthesis. When the locus of the laser beam is not on the incident surface, the incident angle of the projection of the locus onto the incident surface is defined as θ. If the laser light is incident at this incident angle θ, the reflected light from the surface of the substrate and the reflected light from the back surface of the substrate do not interfere with each other, and uniform laser light irradiation can be performed. In the above discussion, the refractive index of the substrate was considered as 1. Actually, in many cases, the refractive index of the substrate is around 1.5, and if this value is taken into consideration, a calculated value larger than the angle calculated in the above discussion can be obtained. However, since the energy at both ends in the longitudinal direction of the beam spot is attenuated, the influence of interference in this portion is small, and the effect of interference attenuation can be sufficiently obtained with the above calculated value. The above inequality for θ does not apply to anything other than the substrate being translucent to the laser beam.
[0101]
The configuration of this embodiment can be implemented by freely combining with the first embodiment.
[0102]
(Example 3)
In this embodiment, a method for manufacturing a semiconductor device using the laser irradiation apparatus or the laser irradiation method of the present invention will be described. Note that in this embodiment, a light-emitting device is described as an example of one of the semiconductor devices; however, a semiconductor device that can be manufactured using the present invention is not limited thereto, and a liquid crystal display device or other semiconductor devices is used. It may be.
[0103]
The light emitting device is a semiconductor device in which means for supplying current to a light emitting element and the light emitting element are provided in each of a plurality of pixels. A light emitting element (OLED: Organic Light Emitting Diode) includes a layer containing an electroluminescent material (hereinafter referred to as an electroluminescent layer) from which luminescence generated by applying an electric field is obtained, an anode layer, a cathode layer, have. The electroluminescent layer is provided between the anode and the cathode, and is composed of a single layer or a plurality of layers. In some cases, these layers contain an inorganic compound.
[0104]
First, as shown in FIG. 14A, in this embodiment, a substrate 500 made of glass such as barium borosilicate glass or alumino borosilicate glass is used. Note that as the substrate 500, a quartz substrate, a silicon substrate, a metal substrate, or a stainless steel substrate on which an insulating film is formed may be used. Further, a plastic substrate having heat resistance that can withstand the processing temperature of this embodiment may be used.
[0105]
Next, a base film 501 made of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed over the substrate 500 by a known means (a sputtering method, an LPCVD method, a plasma CVD method, or the like). In this embodiment, a single-layer base film is used as the base film 501, but a structure in which two or more insulating films are stacked may be used.
[0106]
Next, an amorphous semiconductor film 502 having a thickness of 50 nm was formed on the base film 501 by a plasma CVD method. Although it depends on the amount of hydrogen contained in the amorphous semiconductor film, it is preferable that the dehydrogenation treatment is performed by heating at 400 to 550 ° C. for several hours, and the crystallization step is performed with the amount of hydrogen contained being 5 atom% or less. . In addition, the amorphous semiconductor film may be formed by another manufacturing method such as a sputtering method or an evaporation method, but it is desirable to sufficiently reduce impurity elements such as oxygen and nitrogen contained in the film.
[0107]
Note that not only silicon but also silicon germanium can be used for the semiconductor film. When silicon germanium is used, the concentration of germanium is preferably about 0.01 to 4.5 atomic%.
[0108]
Here, the base film 501 and the amorphous semiconductor film 502 are both formed by a plasma CVD method. At this time, the base film 501 and the amorphous semiconductor film 502 are continuously formed in a vacuum. Also good. After forming the base film 501, once the process is not exposed to the air atmosphere, the surface contamination can be prevented, and the variation in characteristics of the manufactured TFT can be reduced.
[0109]
Next, as shown in FIG. 14B, the amorphous semiconductor film 502 is crystallized by a laser crystallization method. The laser crystallization method is performed using the laser irradiation apparatus or the laser irradiation method of the present invention. Of course, not only the laser crystallization method but also other known crystallization methods (thermal crystallization method using RTA or furnace annealing furnace, thermal crystallization method using metal element to promote crystallization, etc.) You may go.
[0110]
When the amorphous semiconductor film is crystallized, a crystal having a large grain size can be obtained by using a solid-state laser capable of continuous oscillation and using the second to fourth harmonics of the fundamental wave. Typically, Nd: YVO _Four It is desirable to use the second harmonic (532 nm) or the third harmonic (355 nm) of the laser (fundamental wave 1064 nm). Specifically, continuous wave YVO _Four Laser light emitted from the laser is converted into a harmonic by a non-linear optical element to obtain laser light with an output of 10 W. Also, YVO in the resonator _Four There is also a method of emitting harmonics by inserting a crystal and a nonlinear optical element. Preferably, the laser beam is shaped into a rectangular or elliptical shape on the irradiation surface by an optical system, and the object to be processed is irradiated. The energy density at this time is 0.01 to 100 MW / cm. ² Degree (preferably 0.1-10 MW / cm ² )is required. Then, irradiation is performed by moving the amorphous semiconductor film 502 relative to the laser light at a speed of about 10 to 2000 cm / s.
[0111]
Note that pulsed or continuous wave gas laser or solid-state laser can be used for laser irradiation. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. _Four Laser, YLF laser, YAlO _Three Laser, glass laser, ruby laser, alexandride laser, Ti: sapphire laser, Y ₂ O _Three Etc. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. _Four , YLF, YAlO _Three Lasers using crystals such as can also be used. The fundamental wave of the laser differs depending on the material to be doped, and a laser beam having a fundamental wave of about 1 μm can be obtained. The harmonic with respect to the fundamental wave can be obtained by using a nonlinear optical element.
[0112]
Crystallinity is improved by the laser crystallization described above, and a crystalline semiconductor film 503 is formed.
[0113]
Next, the crystalline semiconductor film 503 is patterned into a desired shape to form island-shaped semiconductor films 504 to 506 to be active layers of the TFT (FIG. 14C). Note that after forming the active layers 504 to 506, a small amount of impurity element (boron or phosphorus) may be doped in order to control the threshold value of the TFT.
[0114]
Next, as shown in FIG. 15A, a gate insulating film 507 containing silicon oxide or silicon nitride as a main component was formed so as to cover the active layers 504 to 506. In this example, TEOS (Tetraethyl Orthosilicate) and O ₂ And a reaction pressure of 40 Pa, a substrate temperature of 300 to 400 ° C., a high frequency (13.56 MHz), and a power density of 0.5 to 0.8 W / cm. ² Was discharged to form a silicon oxide film. The silicon oxide film thus manufactured can obtain good characteristics as a gate insulating film by subsequent thermal annealing at 400 to 500 ° C. Aluminum nitride can be used as the gate insulating film. Aluminum nitride has a relatively high thermal conductivity and can effectively diffuse the heat generated in the TFT. In addition, after forming silicon oxide or silicon oxynitride which does not contain aluminum, a laminate of aluminum nitride may be used as the gate insulating film.
[0115]
Then, as illustrated in FIG. 15B, a conductive film is formed to a thickness of 100 to 500 nm over the gate insulating film 507 and patterned to form gate electrodes 508 to 510.
[0116]
In this embodiment, the gate electrode is formed of an element selected from Ta, W, Ti, Mo, Al, and Cu, or an alloy material or a compound material containing the element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. Further, instead of a single conductive film, a conductive film composed of a plurality of layers may be stacked.
[0117]
For example, a combination of forming the first conductive film with tantalum nitride (TaN) and the second conductive film with W, forming the first conductive film with tantalum nitride (TaN), and forming the second conductive film with Al It is preferable that the first conductive film is formed of tantalum nitride (TaN) and the second conductive film is formed of Cu. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus, or an AgPdCu alloy may be used as the first conductive film and the second conductive film.
[0118]
The structure is not limited to the two-layer structure, and for example, a three-layer structure in which a tungsten film, an aluminum-silicon alloy (Al-Si) film, and a titanium nitride film are sequentially stacked may be employed. In the case of a three-layer structure, tungsten nitride may be used instead of tungsten, or an aluminum / titanium alloy film (Al—Ti) is used instead of an aluminum / silicon alloy film (Al—Si) film. Alternatively, a titanium film may be used instead of the titanium nitride film.
[0119]
Note that it is important to select an optimum etching method and etchant type depending on the material of the conductive film.
[0120]
Next, a step of adding an n-type impurity element is performed to form n-type impurity regions 512 to 517. Here, phosphine (PH _Three ) Using an ion doping method.
[0121]
Next, as shown in FIG. 15C, a step of covering the region where the n-channel TFT is formed with a resist mask 520 and adding a p-type impurity element to the region where the p-channel TFT is formed. P-type impurity regions 518 and 519 were formed.
Here, diborane (B ₂ H ₆ ) Using an ion doping method.
[0122]
Then, for the purpose of controlling the conductivity type, a step of activating the impurity element added to each island-like semiconductor layer is performed. This step is performed by a thermal annealing method using a furnace annealing furnace. In addition, a laser annealing method or a rapid thermal annealing method (RTA method) can be applied. In the thermal annealing method, the oxygen concentration is 1 ppm or less, preferably 0.1 ppm or less in a nitrogen atmosphere at 400 to 700 ° C., typically 500 to 600 ° C. In this example, the temperature is 500 ° C. for 4 hours. Heat treatment is performed. However, when the gate electrodes 508 to 510 are vulnerable to heat, activation is preferably performed after an interlayer insulating film (having silicon as a main component) is formed in order to protect wirings and the like.
[0123]
In the case of using a laser annealing method, it is possible to use a laser used for crystallization. In the case of activation, the moving speed is the same as that of crystallization, and 0.01-100 MW / cm. ² Degree (preferably 0.01 to 10 MW / cm ² ) Energy density is required. Further, a continuous wave laser may be used for crystallization, and a pulsed laser may be used for activation.
[0124]
Further, a heat treatment is performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen to perform a step of hydrogenating the island-shaped semiconductor layer. This step is a step of terminating dangling bonds in the semiconductor layer with thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.
[0125]
Next, as shown in FIG. 15D, a first inorganic insulating film 521 made of silicon oxynitride having a thickness of 10 to 200 nm is formed by a CVD method. Note that the first inorganic insulating film is not limited to the silicon oxynitride film, and may be any inorganic insulating film containing nitrogen that can prevent moisture from entering and leaving the organic resin film to be formed later. Aluminum nitride or aluminum oxynitride can be used. Note that aluminum nitride has a relatively high thermal conductivity, and can effectively diffuse the heat generated in a TFT, a light emitting element, or the like.
[0126]
Next, an organic resin film 522 made of a positive photosensitive organic resin is formed on the first inorganic insulating film 521. In this embodiment, the organic resin film 522 is formed using positive photosensitive acrylic, but the present invention is not limited to this.
[0127]
In this embodiment, positive photosensitive acrylic is applied by a spin coating method, and is baked to form the organic resin film 522. The film thickness of the organic resin film 522 is set to about 0.7 to 5 μm (more preferably 2 to 4 μm) after firing.
[0128]
Next, the part which wants to form an opening part is exposed using a photomask. And after developing with the developing solution which has TMAH (tetramethylammonium hydroxide) as a main component, a board | substrate is dried and baking for about 1 hour at 220 degreeC is performed. Then, as shown in FIG. 15D, an opening is formed in the organic resin film 522, and the first inorganic insulating film 521 is partially exposed in the opening.
[0129]
Note that since positive photosensitive acrylic is colored light brown, a decoloring process is performed when light emitted from the light emitting element is directed toward the substrate. In this case, the entire photosensitive acrylic after development is exposed again before baking. The exposure at this time is such that a slightly stronger light is applied or the irradiation time is extended compared to the exposure for forming the opening so that the exposure is performed completely. For example, when decolorizing a positive acrylic resin with a thickness of 2 μm, multi-wavelength light consisting of g-line (436 nm), h-line (405 nm) and i-line (365 nm), which is the spectrum light of an ultrahigh pressure mercury lamp, is used. When using the same magnification projection exposure apparatus (specifically, MPA manufactured by Canon), irradiation is performed for about 60 seconds. By this exposure, the positive acrylic resin is completely decolorized.
[0130]
In this embodiment, baking is performed at 220 ° C. after development. However, baking may be performed at a low temperature of about 100 ° C. as a pre-bake after development and then baking at a high temperature of 220 ° C.
[0131]
Then, as shown in FIG. 16A, the second inorganic insulating film made of silicon nitride is formed by RF sputtering, covering the opening from which the first inorganic insulating film 521 is partially exposed and the organic resin film 522. A film 523 is formed. The film thickness of the second inorganic insulating film 523 is desirably about 10 to 200 nm. The second inorganic insulating film is not limited to a silicon oxynitride film, and may be any inorganic insulating film containing nitrogen that can suppress the entry and exit of moisture into the organic resin film 522. For example, silicon nitride, aluminum nitride Alternatively, aluminum oxynitride can be used.
[0132]
Note that in the silicon oxynitride film or the aluminum oxynitride film, the ratio of atomic% of oxygen and nitrogen is greatly related to the barrier property. The higher the ratio of nitrogen to oxygen, the higher the barrier properties. Specifically, it is desirable that the ratio of nitrogen is higher than the ratio of oxygen.
[0133]
A film formed using an RF sputtering method has high density and excellent barrier properties. For example, in the case of forming a silicon oxynitride film, the RF sputtering is performed using a Si target, N ₂ , Ar, N ₂ O is flowed so that the gas flow ratio is 31: 5: 4, and the film is formed at a pressure of 0.4 Pa and a power of 3000 W. For example, when a silicon nitride film is formed, N in the chamber is formed with a Si target. ₂ , Ar is allowed to flow so that the gas flow ratio is 20:20, the pressure is 0.8 Pa, the power is 3000 W, and the film formation temperature is 215 ° C.
[0134]
The organic resin film 522, the first inorganic insulating film 521, and the second inorganic insulating film 523 form a first interlayer insulating film.
[0135]
Next, as illustrated in FIG. 16A, a resist mask 524 is formed in the opening of the organic resin film 522, and the gate insulating film 507, the first inorganic insulating film 521, and the second inorganic insulating film 523 are dry-dried. Contact holes are formed using an etching method.
[0136]
Due to the opening of the contact hole, the impurity regions 512 to 515, 518, and 519 are partially exposed. The conditions for this dry etching are appropriately set depending on the materials of the gate insulating film 507, the first inorganic insulating film 521, and the second inorganic insulating film 523. In this embodiment, silicon oxide is used for the gate insulating film 507, silicon oxynitride is used for the first inorganic insulating film 521, and silicon nitride is used for the second inorganic insulating film 523. _Four , O ₂ Etch the second inorganic insulating film 523 made of silicon nitride and the first inorganic insulating film 521 made of silicon oxynitride using He as an etching gas, and then CHF _Three Is used to etch the gate insulating film 507 made of silicon oxide.
[0137]
It is important to prevent the organic resin film 522 from being exposed in the opening during etching.
[0138]
Next, a conductive film is formed over the second inorganic insulating film 523 so as to cover the contact hole, and patterned to form wirings 526 to 531 connected to the impurity regions 512 to 515, 518, and 519. (FIG. 16B).
[0139]
In the present embodiment, a conductive film having a three-layer structure in which a Ti film is formed on the second inorganic insulating film 523, an Al film of 300 nm, and a Ti film of 150 nm are continuously formed by sputtering. It is not limited to. A single-layer conductive film may be formed, or a conductive film including a plurality of layers other than three layers may be formed. Further, the material is not limited to this.
[0140]
For example, after forming a Ti film, a conductive film in which an Al film containing Ti is stacked may be used, or after forming a Ti film, a conductive film in which an Al film containing W is stacked may be used. .
[0141]
Next, an organic resin film to be a bank is formed on the second inorganic insulating film 523. In this embodiment, positive photosensitive acrylic is used, but the present invention is not limited to this. In this embodiment, an organic resin film is formed by applying positive photosensitive acrylic by a spin coating method and baking it. The film thickness of the organic resin film is about 0.7 to 5 μm (more preferably 2 to 4 μm) after firing.
[0142]
Next, the part which wants to form an opening part is exposed using a photomask. And after developing with the developing solution which has TMAH (tetramethylammonium hydroxide) as a main component, a board | substrate is dried and baking for about 1 hour at 220 degreeC is performed. Then, a bank 533 having an opening is formed as shown in FIG. 16C, and the wirings 529 and 531 are partially exposed in the opening.
[0143]
Note that since positive photosensitive acrylic is colored light brown, a decoloring process is performed when light emitted from the light emitting element is directed toward the substrate. The decoloring process is performed in the same manner as the decoloring process performed on the organic resin film 522.
[0144]
By using a photosensitive organic resin for the bank, the cross section of the opening can be rounded, so that the coverage of the electroluminescent layer and cathode to be formed later can be improved and the light emitting area is reduced. Defects called can be reduced.
[0145]
Then, as shown in FIG. 17A, a third inorganic insulating film 534 made of silicon nitride is formed by RF sputtering, covering the openings where the wirings 529 and 531 are partially exposed and the bank 533. Film. The thickness of the third inorganic insulating film 534 is desirably about 10 to 200 nm. The third inorganic insulating film 534 is not limited to a silicon oxynitride film, and may be any inorganic insulating film containing nitrogen that can prevent moisture from entering and exiting the bank 533. For example, silicon nitride, aluminum nitride, or Aluminum oxynitride can be used.
[0146]
Note that in the silicon oxynitride film or the aluminum oxynitride film, the ratio of atomic% of oxygen and nitrogen is greatly related to the barrier property. The higher the ratio of nitrogen to oxygen, the higher the barrier properties. Specifically, it is desirable that the ratio of nitrogen is higher than the ratio of oxygen.
[0147]
Then, a resist mask 535 is formed in the opening of the bank 533, and a contact hole is formed in the third inorganic insulating film 534 using a dry etching method.
[0148]
Due to the opening of the contact hole, the wirings 529 and 531 are partially exposed. The conditions for this dry etching are appropriately set depending on the material of the third inorganic insulating film 534. In this embodiment, since silicon nitride is used for the third inorganic insulating film 534, CF _Four , O ₂ The third inorganic insulating film 534 made of silicon nitride is etched using He as an etching gas.
[0149]
It is important that the bank 533 is not exposed in the opening during etching.
[0150]
Next, a transparent conductive film, for example, an ITO film is formed to a thickness of 110 nm, and patterning is performed to form a pixel electrode 540 in contact with the wiring 531 and a lead wiring 541 for obtaining a current generated in the diode. Alternatively, a transparent conductive film in which 2 to 20% zinc oxide (ZnO) is mixed with indium oxide may be used. This pixel electrode 540 serves as an anode of the light emitting element (FIG. 17B).
[0151]
Next, an electroluminescent layer 542 is formed on the pixel electrode 540 by an evaporation method, and a cathode (MgAg electrode) 543 is further formed by an evaporation method. At this time, it is preferable that the pixel electrode 540 is subjected to heat treatment to completely remove moisture before forming the electroluminescent layer 542 and the cathode 543. In this embodiment, an MgAg electrode is used as the cathode of the OLED. However, other known materials such as Ca, Al, CaF, MgAg, and AlLi may be used as long as the conductive film has a low work function.
[0152]
Note that when AlLi is used as the cathode, the third interlayer insulating film 534 containing nitrogen can prevent Li in AlLi from entering the substrate side from the third interlayer insulating film 534.
[0153]
Note that a known material can be used for the electroluminescent layer 542. In this embodiment, a two-layer structure including a hole transporting layer and a light emitting layer is an electroluminescent layer, but any one of a hole injection layer, an electron injection layer, and an electron transport layer is provided. In some cases. As described above, various examples of combinations have already been reported, and any of the configurations may be used. For example, SAlq or CAlq may be used as the electron transport layer or the hole blocking layer.
[0154]
Note that the thickness of the electroluminescent layer 542 may be 10 to 400 nm (typically 60 to 150 nm), and the thickness of the cathode 543 may be 80 to 200 nm (typically 100 to 150 nm).
[0155]
Thus, a light emitting device having a structure as shown in FIG. 17B is completed. In FIG. 17B, reference numeral 550 denotes a pixel portion, and 551 corresponds to a driver circuit portion. In the pixel portion 550, a portion 552 where the pixel electrode 540, the electroluminescent layer 542, and the cathode 543 overlap corresponds to an OLED.
[0156]
Note that the structure and specific manufacturing method of the TFT shown in this embodiment are merely examples, and the present invention is not limited to this structure.
[0157]
Actually, when completed up to FIG. 17B, a protective film (laminate film, UV curable resin film, etc.) or a translucent cover material with high air tightness and low outgassing so as not to be exposed to the outside air. It is preferable to package (enclose). At that time, if the inside of the cover material is made an inert atmosphere or if a hygroscopic material (for example, barium oxide) is arranged inside, the reliability of the OLED is improved.
[0158]
Note that this embodiment can be freely combined with Embodiment 1 or 2.
[0159]
Example 4
In this embodiment, the relationship between the distance between the centers of laser beams and the energy density when the laser beams are superimposed will be described. For ease of explanation, a case where no slit is provided will be described.
[0160]
In FIG. 18, the distribution of energy density in the direction of the central axis of each laser beam is indicated by a solid line, and the distribution of energy density of the synthesized laser beam is indicated by a broken line. The value of the energy density in the central axis direction of the laser light generally follows a Gaussian distribution.
[0161]
1 / e of peak value in laser light before synthesis ² Let X be the distance between the peaks when the distance in the central axis direction satisfying the above energy density is 1. In the synthesized laser light, Y is the percent increment of the peak value after the synthesis and the average value of the valley values. The relationship between X and Y determined by simulation is shown in FIG. In FIG. 19, Y is expressed as a percentage.
[0162]
In FIG. 19, the energy difference Y is expressed by an approximate expression of Expression 1 below.
[0163]
[Formula 1]
Y = 60-293X + 340X ² (X is the larger of the two solutions)
[0164]
According to Equation 1, for example, when it is desired to make the energy difference about 5%, it can be understood that X≈0.584. Ideally, Y = 0, but since the length of the laser beam is shortened, it is better to determine X in balance with the throughput.
[0165]
Next, the allowable range of Y will be described. FIG. 20 shows YVO with respect to the beam width in the central axis direction when the laser beam has an elliptical shape. _Four The distribution of laser output (W) is shown. The region indicated by hatching is the range of output energy necessary for obtaining good crystallinity. In the case of this embodiment, the output energy of the synthesized laser beam is within the range of 3.5 to 6 W. I know it ’s good.
[0166]
When the maximum value and the minimum value of the output energy of the laser light after synthesis enter the limit of the output energy range necessary for obtaining good crystallinity, the energy difference Y that provides good crystallinity is maximized. Accordingly, in the case of FIG. 20, the energy difference Y is ± 26.3%, and it can be seen that good crystallinity can be obtained if the energy difference Y is within the above range.
[0167]
Note that the range of output energy necessary to obtain good crystallinity varies depending on how far the crystallinity is judged to be good, and the distribution of output energy also varies depending on the shape of the laser beam. The allowable range of Y is not necessarily limited to the above value. The designer needs to appropriately determine the range of output energy necessary for obtaining good crystallinity, and set the allowable range of the energy difference Y from the distribution of the output energy of the laser used.
[0168]
This embodiment can be implemented in combination with the first to third embodiments.
[0169]
(Example 5)
In this embodiment, a method of crystallizing a semiconductor film after patterning into a strip shape and then scanning with laser light along the long axis direction of the strip will be described.
[0170]
FIG. 21A shows a state in which laser light is scanned over the semiconductor film 901 patterned in a strip shape. The scanning direction of the laser light is along the long axis direction of the strip. Specifically, the strip-shaped semiconductor film 901 has a width in the direction perpendicular to the major axis of about several μm to several tens of μm, and is laid out with an interval of about several hundred nm to several μm.
[0171]
Then, the laser beam is scanned so that the edge of the laser beam does not overlap with the strip-shaped semiconductor film, but just fits between the semiconductor films. By separating each other, heat can be prevented from diffusing in the direction of the central axis of the laser beam during crystallization, and regions with poor crystallinity distributed near the edge of the laser beam can be diffused. It can be suppressed as much as possible.
[0172]
Note that when laser light is irradiated after patterning the semiconductor film, microcrystals are formed at the corners of the semiconductor film. For example, in a pulsed excimer laser, although it depends on the thickness of the semiconductor film, many crystallites with a grain size of less than 0.1 μm are seen near the corner of the semiconductor film, compared to the crystal grains formed in the center. The particle size tends to be small. This is thought to be because the way of diffusion of heat applied by the laser beam to the substrate differs between the vicinity of the edge and the central portion. However, the microcrystalline region formed at the edge of these semiconductor films is formed by irradiating laser light without patterning, and by thermally diffusing the portion near the edge of the laser light where the energy density is weak. Since it is narrower than the region of the microcrystal, a region where the crystallinity obtained is actually good can be widely used.
[0173]
Next, as shown in FIG. 21B, after crystallization with laser light, the strip-shaped semiconductor film is further patterned to form an island-shaped semiconductor film 902.
[0174]
Note that if the strip-shaped semiconductor film is not sufficiently spaced, it will deform by gravity when melted by laser light irradiation, and will adhere to each other, making it impossible to obtain the above effects There is sex. However, when the surface on which the semiconductor film is formed is turned down at the time of laser light irradiation, adhesion between adjacent semiconductor films can be prevented, and the interval between the strip-shaped semiconductor films can be further narrowed.
[0175]
This embodiment can be implemented by freely combining with the first to fourth embodiments.
[0176]
【The invention's effect】
In the present invention, by combining laser beams oscillated from a plurality of laser oscillation devices, it is possible to compensate for the weak energy density of each laser beam. Therefore, rather than combining laser beams emitted from a plurality of laser oscillation devices without using them individually, a region of the laser beam having an energy density required for crystallization is widened, and the substrate processing efficiency is increased. Can be increased.
[0177]
Further, in the present invention, a slit is used to cut a region of the synthesized laser light where the energy density does not reach a predetermined value in the scanning direction. With the above structure, the average value of the energy density of the laser light in the scanning direction can be increased, and the irradiation time of the laser light at any point on the object to be processed can be suppressed. Therefore, the crystallinity of the semiconductor film can be improved while suppressing the substrate from being heated.
[Brief description of the drawings]
FIG. 1 shows a structure of a laser irradiation apparatus of the present invention.
FIG. 2 is a diagram showing the shape of laser light and the distribution of energy density.
FIG. 3 is a diagram showing a positional relationship between laser light and a slit.
FIG. 4 is a diagram showing a positional relationship between laser light and a slit.
FIG. 5 is a diagram showing a direction in which laser light moves in an object to be processed.
FIG. 6 is a diagram showing a direction in which laser light moves in an object to be processed.
FIG. 7 illustrates a crystallization mechanism using an SLS method.
FIG. 8 is a diagram illustrating a crystallization mechanism using an SLS method.
FIG. 9 is a diagram of an optical system of a laser irradiation apparatus.
FIG. 10 is a diagram of an optical system of a laser irradiation apparatus.
FIG. 11 is a diagram of an optical system of a laser irradiation apparatus.
FIG. 12 is a diagram of an optical system of a laser irradiation apparatus.
FIG. 13 is a diagram of an optical system of a laser irradiation apparatus.
14A and 14B illustrate a method for manufacturing a semiconductor device using a laser irradiation apparatus of the present invention.
FIGS. 15A and 15B illustrate a method for manufacturing a semiconductor device using a laser irradiation apparatus of the present invention. FIGS.
FIGS. 16A to 16C illustrate a method for manufacturing a semiconductor device using the laser irradiation apparatus of the present invention. FIGS.
FIGS. 17A to 17C illustrate a method for manufacturing a semiconductor device using a laser irradiation apparatus of the present invention. FIGS.
FIG. 18 is a diagram showing an energy density distribution in a central axis direction of superimposed laser beams.
FIG. 19 is a diagram showing the relationship between the distance between the centers of laser beams and the energy difference.
FIG. 20 is a diagram showing the distribution of output energy in the direction of the central axis of laser light.
FIG. 21 is a diagram showing an embodiment of the laser irradiation method of the present invention.

Claims (16)

A semiconductor film is formed over a light-transmitting substrate,
A plurality of first laser light outputted from the first laser oscillation device one surface to a plurality of said substrate is condensed by the first optical system, a plurality on the surface opposite to the one surface of the substrate A plurality of second laser beams output from the second laser oscillation device are condensed by the second optical system and partially overlap each other,
Limiting the width of the superimposed first laser light and second laser light in the moving direction on the substrate with a slit,
A semiconductor device characterized in that the semiconductor film is crystallized by irradiating the semiconductor film with the first laser light and the second laser light with the limited width by moving the substrate. Manufacturing method. A semiconductor film is formed over a light-transmitting substrate,
A plurality of first laser light outputted from the first laser oscillation device one surface to a plurality of said substrate is condensed by the first optical system, a plurality on the surface opposite to the one surface of the substrate A plurality of second laser beams outputted from the second laser oscillation device are condensed by the second optical system and partially overlap each other so that each center is on a straight line,
Limiting the width of the superimposed first laser light and second laser light in the moving direction on the substrate with a slit,
A semiconductor device characterized in that the semiconductor film is crystallized by irradiating the semiconductor film with the first laser light and the second laser light with the limited width by moving the substrate. Manufacturing method. A semiconductor film is formed over a light-transmitting substrate,
A plurality of first laser light outputted from the first laser oscillation device one surface to a plurality of said substrate is condensed by the first optical system, a plurality on the surface opposite to the one surface of the substrate A plurality of second laser beams output from the second laser oscillation device are collected by a second optical system and partially overlap each other so that the major axis of each laser beam draws a straight line,
Limiting the width of the superimposed first laser light and second laser light in the moving direction on the substrate with a slit,
A semiconductor device characterized in that the semiconductor film is crystallized by irradiating the semiconductor film with the first laser light and the second laser light with the limited width by moving the substrate. Manufacturing method. In claim 2 ,
A method for manufacturing a semiconductor device, wherein a straight line obtained by connecting the centers and a direction in which the substrate moves is 10 ° to 80 °. In claim 2 ,
A method for manufacturing a semiconductor device, wherein a straight line obtained by connecting the centers and a direction in which the substrate moves are substantially perpendicular to each other. In claim 3 ,
A method for manufacturing a semiconductor device, wherein a straight line drawn by a major axis of each laser beam and a direction in which the substrate moves are 10 ° or more and 80 ° or less. In claim 3 ,
A method for manufacturing a semiconductor device, wherein a straight line drawn by a major axis of each laser beam and a direction in which the substrate moves are substantially perpendicular to each other. In any one of Claims 1 thru | or 7 ,
The method for manufacturing a semiconductor device, wherein the irradiation with the first laser light and the second laser light is performed in a reduced-pressure atmosphere or an inert gas atmosphere. In any one of claims 1 to 8, wherein the first laser oscillator and the second laser oscillation device, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, a ruby laser, or _{Y 2} A method for manufacturing a semiconductor device, wherein one or more selected from O ₃ are used. In any one of claims 1 to 9, the method for manufacturing a semiconductor device wherein the first laser beam and the second laser light is continuous wave. In any one of claims 1 to 8, wherein the first laser oscillator and the second laser oscillation device, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ lasers, glass lasers, ruby lasers A method for manufacturing a semiconductor device, wherein one or more selected from Alexandride laser, Ti: sapphire laser, or Y ₂ O ₃ are used. In any one of claims 9 to 11, wherein the first laser beam and said second laser beam is a method for manufacturing a semiconductor device which is a second harmonic. In any one of claims 1 to 12, a method for manufacturing a semiconductor device, wherein the number of the first laser oscillation device and the second laser oscillator is 2 to 4. In any one of claims 1 to 13, wherein the first laser beam and the irradiation of the second laser beam, a method for manufacturing a semiconductor device, characterized in that it is carried out using the SLS method. 15. The first laser beam and the second laser beam according to claim 1, wherein the first laser beam and the second laser beam are reflected on one surface of the substrate and on a side opposite to the one surface of the substrate. A method for manufacturing a semiconductor device, wherein reflected light from a surface is incident at an angle that does not interfere with the surface. 16. The manufacturing method of a semiconductor device according to claim 15, wherein the angle is θ ≧ arctan (W / 2d) (W is a length of a short side or a long side of laser light, and d is a thickness of the substrate). Method.

Images